Banner post high authority site any good?

A high authority site (DA 60) that has a lot of organic traffic (its a news site) is asking $50/month for a sidebar banner image. The link is do-follow (I can safely say that they do not know ********/nofollow) and I can have my keyword on the ALT tag.

Besides referral traffic, is this going to affect my site in anyway (bad or good)?

Banner Posting is not that tough task but firstly you need to tell which type of site you need for posting as there are mostly paid banner posting sites available. Free Banner posting sites are not that trustworthy and also generated unethical links to your site. try to use paid banner posting sites as they have a good DA & PA and also will generate ethical links for your website.

please suggest me something new off page techniques.